The use of lathes has long been known for machining axially symmetrical portions of parts of all types. Simply stated, a lathe is operated by fixing, or chucking, a part into the machine. Once chucked, the lathe is powered to rotate the part and a cutting tool is brought into contact with the rotating part to remove material therefrom. Movement of the part within the chuck would halt the process and damage the tool and/or machine. Therefore, a solid grasp of the part by the chuck is important to ensure that the part does not move under the force of the cutting tool. It is also important to avoid marring the part with the chucking fixture. Care must be taken to grasp the part only as tight as necessary to obtain proper mounting and machining of the part without marring. This problem becomes especially troublesome when the portion of the part being chucked has already been machined into its final form because marring of that chucked portion would result in a defective part either for reasons of required tolerances or for mere aesthetic reasons.
With the advent of computers and electronic sensing means has come automated cutting machines in which parts are machined according to a preset program defining the path taken by the cutting tool along the turning part. These automated cutting machines are referred to as Computer Numeric Control machines ("CNC machines"). A typical CNC machine will locate the cutting tool, and the cutting path it takes, to the CNC machine itself; not the part. Therefore, it is important that the part is properly chucked in the CNC machine and to properly locate the part with respect to the CNC machine itself If the part is out of location by, for example, five thousandths of an inch, then the cutting accomplished by the cutting tool will likewise be out of location by five thousandths of an inch. Similarly, because turning machines are used to machine axially symmetric parts, or axially symmetric portions of parts, it is important to align the axis of the part with the rotational axis of the turning fixture and thus the CNC machine. Again, misalignment will result in a defective part. Although CNC machines are capable of producing highly accurate and complex parts, the accuracy of the resulting part is highly dependant upon the proper location of the part to the cutting machine, whether it be a CNC or manually operated.
A special problem often arises when the part comprises a taper on or near the portion of the part which facilitates chucking or locating of the part. Traditional chucking fixtures intended for non-tapered parts often mar the tapered surface and typically present great difficulties in properly locating the part with respect to the cutting machine. The industry thus turned to tapered collets custom machined to chuck on the taper of the part. The collet taper also functioned to locate the part. However, because these collets were custom machined for a specific angle of taper, they were only useful for parts having a taper of that specific angle. Therefore, if a run of parts required identical machining and the parts were identical in every way except for the taper on which they would be located, a separate collet would have to be precision machined for each different taper. Portions of the fixture were disassembled to remove the collet and reasembled to employ a different collet each time a part having a different taper was to be machined. Moreover, because a collet holds the part, a job specific collet must clamp onto the taper of the part with sufficient force to prevent relative movement there between during the cutting process. Marring of the tapered surface would often result. Additionally, the collets wore after extended use such that the part location would change with respect to the turning machine. Parts located by such a worn collet during machining would be defective.